The present invention relates to a truck trailer for hauling gravel, crushed rock, sand, and other particulate matter. In particular, the present invention relates to a truck trailer for hauling particulate or granular materials, which has an internal conveyor system for conveying the particulate matter along the length of the trailer bed, and a movable tailgate assembly mounted at the discharge end of the trailer bed and movable into desired positions beneath the discharge end of the trailer bed to enable the particulate matter to be discharged in discrete piles or spread evenly over a desired area.
Gravel, crushed rock or stone, sand, feed, and other particulate materials typically are transported from a quarry or loading site to a dump site in open bed truck dump trailers that are generally pulled by a semi truck. Once at the dump site, the end of the dump trailer nearest the truck cab generally is raised or lifted so as to cause the material therein to flow toward the rear or discharge end of the dump trailer to dump the particulate material at the site.
Depending on the size of the dump trailer, the dump trailer can be extended or raised up to as much as 30 feet in the air. The problem with most conventional dump trailers is that when they are raised to their fully extended position, they tend to create a dangerous, top-heavy condition, especially with heavier loads such as crushed rock or gravel. As a result, there is a significant danger of tipping or rolling over when the dump trailers are in their raised positions, creating a hazard to both the equipment and the operators. The danger of tipping or rolling over is further increased when the dump trailer is being used to dump materials over uneven or slick ground as is commonly found at construction sites. There is also the danger, especially along roadways with overhanging power lines, that the raised dump trailer could come into contact with such overhanging power lines as the operator has to move the truck forward to complete the dumping of the materials, creating a danger of electrocution.
In addition, when conventional dump trailers are raised so as to dump their load of material, typically all of the material tends to flow to the rear or discharge end of the trailer under the force of gravity. As a result, there is little or no ability for the operator to control the distribution of the material, but rather the material instead tends to be dumped in a large uncontrolled mass. It is also sometimes necessary to jog or bounce the trailer to dislodge any additional particulate materials and to insure that all of the material is dumped from the truck as the discharge end becomes blocked by the growing pile of material. The shifting of the load toward the rear of the dump trailer further puts greater stress on the rear of the trailer and on the ability of the truck to pull such a load, especially when going up hills.
Attempts have been made in the art to develop conveyor systems for truck trailers that will enable the discharge of granular or particulate materials from the dump trailer without requiring the trailer to be raised for dumping of the materials. For example, U.S. Pat. No. 4,923,359 of Petri, et al. and U.S. Pat. No. 5,102,285 of Gust show gravel hauling or delivery trailers having conveyors for urging or conveying the particulate materials contained therein from one end of the trailer to the rear of the trailer for discharge. While such assemblies provide a mechanism for discharging granular or particulate materials without requiring the bed of the trailer to be lifted or dumping the material, such conveyor systems are limited in their ability to convey the material and further in their ability to control the discharge of the material to enable spreading of the material across a desired area or for dumping of the material in discrete piles as needed or desired without requiring additional attachments or devices.
Accordingly, it can be seen that a need exists for a truck trailer for hauling and distributing gravel, crushed stone, and other particulate materials, which enables safe and efficient distribution of the material with the ability to control such distribution for even spreading over a desired area or dumping in discrete piles as needed.
Briefly described, the present invention relates to a truck trailer of the type designed to be attached to and pulled behind a truck or tractor rig for hauling gravel, crushed rock, sand, feed and other particulate or granular materials. The truck trailer includes a trailer body having sloped side walls, a front end and a rear or discharge end, which define a basin or bin in which the particulate materials, such as gravel, are contained. A first conveyor is positioned on the bottom of the trailer body that extends from a first end at or adjacent the front end of the trailer body, and a second or discharge end positioned at an intermediate point along the length of the trailer body. A second conveyor assembly is mounted within the trailer body, extending upwardly at an angle with respect to the first conveyor. The second conveyor includes a first or lower end that is positioned beneath the discharge end of the first conveyor, and an upper or discharge end positioned at the discharge end of the trailer body.
Each of the conveyors includes a pair of parallel conveyor chains extending about an endless, substantially elliptical path and having a series of cross-braces at spaced intervals that extend between and are attached to each of the chains. Flexible conveyor members, or belts, typically formed from rubber or similar flexible materials are mounted to the cross-braces with the conveying members slightly overlapping so that the conveying members can flex and roll over to urge the gravel from the first conveyor onto the second conveyor and from the second conveyor out of the discharge end of the trailer body. The first and second conveyors thus form a movable floor for the trailer body, with the first conveyor forming a first movable conveyor section and the second conveyor forming a second movable floor section.
Each of the conveyors is connected to a drive system for rotating the conveyors about their conveying paths. Typically, the drive system includes a series of drive motors mounted at the second or discharge ends of the first and second conveyors, connected to the conveyors in a driving relationship. The motors can be electric motors, although typically hydraulic motors will be used, with the motors being powered through hydraulic lines connected to hydraulic pumps that are in turn connected to the power take-off assembly of the truck. The drive motors for each of the first and second conveyors generally are arranged in pairs of motors mounted on opposite sides of the trailer body and connected to drive sprockets for each of the conveyors. Separate drive controls are provided for the drive motors for each of the conveyors. The speed of the motors can be controlled using the controls, with the second conveyor generally being run at a constant, full speed and the first conveyor run at varying speeds as necessary.
A movable tailgate assembly is mounted at the rear of the trailer body for receiving the gravel, crushed rock or other particulate materials from the second conveyor. The tailgate assembly includes a tailgate that is movable between a lowered, non-engaging position and a fully raised, spreading position. The tailgate includes an elongated body and a series of spaced partitions or dividers for channeling or dividing the flow of particulate materials across the tailgate for spreading the material over a desired area. A hydraulic cylinder is pivotally mounted to the truck frame and is pivotally attached to the tailgate. A hydraulic control is provided for controlling the operation of the hydraulic cylinder of the tailgate assembly so as to cause the tailgate to be moved between its raised and lowered positions as needed for discharging the particulate material in discrete piles or spreading the particulate material over a desired area.
Accordingly, the trailer body generally is loaded with sand, gravel, crushed rock or other particulate material and is driven to a job site for the discharge of the material. At the site, the controls for the first and second conveyors are engaged so as to urge the particulate material toward the discharge end of the trailer body. Depending upon the manner in which the material is to be discharged, the tailgate is left in its lowered, non-engaging position or raised to a desired spreading position. If the material is to be simply dumped in discrete piles, the tailgate is left in its lowered position and the particulate material is urged off the second or discharge end of the conveyor into a pile below the discharge end of the trailer. If the material is to be spread over a desired area, the tailgate is raised to a desired spreading position depending on the area to be covered, and the material is fed onto the tailgate which causes the material to be spread across a wider area as the truck is moved forward such as for applying a layer of crushed rock along a roadbed for paving.
Various objects, features and advantages of the present invention will become apparent to those skilled in the area upon reading the following specification when taken in conjunction with the accompanying drawings.